I'm all in favour of requiring isl and enabling graphite by default, but would suggest to enable it with -Ofast instead.
One reason is that certainly extracting testcases from a PGO build is more difficult, and initially there will certainly be miscompiles with graphite (CP2K is right now). Furthermore, unless graphite is particularly effective with PGO (does it use average loop trip counts already?), I don't see a particular connection. Joost
